The present invention relates to methods of creating a self-documenting logfile of events which occur during the operation of a computer-controlled mechanical device, and more specifically, to methods for verification and detection of alterations to the self-documenting logfile.
Modern advances in computer related technologies have provided application programs which allow users of mechanical devices to operate the devices via computer control. Such computer control has numerous advantages including time savings and a general reduction in operational error.
One example of such an application program is disclosed in the above-referenced co-pending patent application for image-oriented computer control of a supercritical fluid extractor. A partially schematic supercritical fluid extractor is shown in FIG. 1. Typically, the extractor 10 will include the following components: an analyte trap 12, an extraction chamber 13, extraction fluids 14, fluid delivery means 15, fraction output means 16, a keyboard 17, and rinse solvents 18. The extractor 10 is electrically interfaced to a computer 2 which runs the image-oriented extractor applications software.
The image-oriented applications program, in brief, displays an image depicting the supercritical fluid extractor on a monitor 8 and accepts instruction inputs from the user pertaining to the desired function to be performed, via a keyboard 4 or mouse 6. This input triggers the application programs to display status information related to the functional component selected by the user. The applications program then permits the user to modify the extractor's operation or status accordingly.
Initially, the extractor 10 is displayed on the monitor 8 as shown in FIG. 2. The user then moves a cursor (not shown) to one of the extractor's functional components and selects this component by pressing a button on the mouse. For instance, if the user selects the extraction chamber functional component 13 in FIG. 1, a new screen, depicted in FIG. 3, will be displayed providing the user with the extraction chamber status. The user may modify the extraction chamber parameters, for example by changing the temperature setting 64. This may be accomplished by moving the cursor to the temperature setting 64, pressing a button on the mouse and entering the desired temperature setting. Alternatively, the user may select the increment arrow 61 or the decrement arrow 62, causing the temperature setting 64 to change by 1.degree. C. in the corresponding direction.
As will be appreciated by those of ordinary skill, for the operational status of the mechanical device or its functional components to be accurately displayed, it will be necessary that an appropriate sensor be present in the mechanical device. Such sensors detect a given condition, such as temperature, and convey this information to a computer or other processor so that it may be displayed on a display screen. Examples of suitable sensors are pressure sensors, optical sensors of quantifiable parameters such as absorption, transmittance and fluorescence, and electrodes which detect changes in, for example, pH and electric potential.
Likewise, for modification of an operating parameter to be implemented in the operation of the mechanical device, an actuation means must be present in that mechanical device to drive the device to the new, selected operational status. In the supercritical fluid extractor described above with reference to FIGS. 1-3, for example, drivers change fluid flow, dispense fluids, and change valve positions.
As further understood by those of ordinary skill, most devices have a performance standard or other routine against which results are measured. For example, most analytical laboratory testing must conform to Good Laboratory Practices (GLP) and general-laboratory record keeping requirements. Typically, these requirements are satisfied by hand recording data or by manually updating a database containing each operation performed by the computer-controlled mechanical device. The problems encountered using these techniques are well known. For instance, potentially valuable information might not be recorded due to a failure to update the record. The resulting record might be inaccurate as a result of recording information incorrectly, or the record or database could be tampered with inadvertently.
Therefore, there is a need for a self-documenting method to record the status and user instructions for a computer-controlled mechanical device in order to comply with standards such as GLP and general laboratory record keeping requirements, so that a chronological history may be reviewed to verify the accuracy of the device's operation and to determine whether the records may have been affected by accidental or inadvertent erasure or tampering attempts.